Very little is known about heme transport in eukaryotes and a heme-specific transport uptake systems have not been identified in yeast. Heme is synthesized in mitochondria, yet the cofactor is used in compartments throughout the cell. Heme is highly hydrophobic and is unlikely to be released into the aqueous environment of the cytosol, suggesting that mechanisms exist for the intracellular trafficking of heme. We are currently characterizing the heme efflux activity of the putative mitochondrial heme exporter of humans, FLVCR1b.